TechfestIIT Bombay

Grippers and lifting

mechanisms

APEXO

Piezoelectric element-

when “pressed” produces voltage and “released”

produces negative voltage.

Circuit- With 2 voltage sources

Carefully observe the hand.

Vaccum grippers

Vaccum power is used to

create grip and so used to

lift objects or even the

robotlift itself.

But this consumes lot of

power.

Types of Vacuum Grippers

Suction cups are very well suited for a wide variety of

needs and circumstances. They can handle plate,

paper, wood – practically any material.

Be it smooth, irregular, bent, porous, airtight,

lightweight, heavy, angled, hot or cold, the

material can be handled by suction cups safely,

gently and quickly.”

Small to

medium

objects

Uneven

objects

Large, heavy

objects

Angular grippers

Angular grippers are less expensive, but the arcing

motion of the jaws may require additional tooling

clearance and will grip at varying points as part width

varies. A parallel gripper is simpler to tool to

compensate for part size variance.

Parallel grippers

Parallel: The gripper jaws move in a parallel

motion in relation to the gripper body. Used in

a majority of applications, parallel grippers are

typically more accurate than other style

grippers.

Pneumatic grippers Controlled by pneumatic solenoid valves, pressure

cylinders

Simple pneumatic gripper

Advantages and Disadvantages

Pneumatic Electric Motor

Hydraulic

Smaller units, quick assembly

High accuracy and repeatability

High strength and high speed

High cycle rate Less floor space Large robots, Takes floor space

– Easy maintenance Low cost Mechanical Simplicity

Easy maintenance Used usually for heavy payloads

Feedback in grippers

Angle feedback or position feedback can be

taken from potentiometers or tactile switches.

Slow

Allows for

misalignment when

grabbing

Extends object as

releasing.

Simple mechanism.

Roller Grip

Grashof condition-In 4 bar

mechanism

If the sum of the shortest and longest link of a planar quadrilateral

linkage is less than or equal to the sum of the remaining two links,

then the shortest link can rotate fully with respect to a neighboring

link. In other words, the condition is satisfied

if S+L ≤ P+Q where S is the shortest link, L is the longest,

and P and Q are the other links.

Gripper with 4 bar mechanism

Intake Rollers

Pulley mechanism for lifting

Sliding section mechanism

Sliding sections that move

linearly

Mostly powered by a winch

pulling on a cable

Similar to the front of a forklift

Advantages

– Able to extend very

far with little space

consumed

– Stable linear path

– Less for driver to

think about

– Simply powered by a

winch

Disadvantages

– Jamming, they jam,

and jamming too.

– Hard to repair

– Require being stored

in a long straight

area

– Do not handle

bending loads well

4-Bar linkages

4 bar mechanism

On unfolding the 4 bar mechanism ,

lifting motion can be produced.

Pros and cons of 4 bar mechanism

Pros– Simple

– Object retains orientation

– 1 joint to power

– Easily programmed

– Provides reach

Cons– Large moments can develop

at the joint location

– Pin Loadings can be high

– Required to lift “outside of the box”

– Can be vulnerable to side hits

Tips– Watch for buckling in lower member

– If possible, counterbalance

– Keep the center of gravity (CG) aft

Vertical Lifts - Scissors Overview

– The scissor lift is unique in that it doesn't use a straight support to raise workers or objects into the air.

– Rather, the scissor lift platform raises when the linked, folding supports underneath it draw together, stretching it upward.

– It can be powered by hydraulics or an electric motor, but it's a bumpy ride to the top.

– The scissor lift's design keeps it from traveling with a constant velocity, instead traveling faster in the middle of its journey and slower with more extension.

THANKS

For your patience